Only 1.50 metres tall, she entered the Olympic Games in Athens as a three-time world champion in the lightest weight division. In the preliminary round, Merleni easily defeated her three opponents, outscoring them 31-0 in only 4 minutes 36 seconds total. She shut out her semi final opponent, Patricia Miranda of the United States, 9-0. In the final, Merleni finally met her match: Japan's Chiharu Icho, the reigning world champion in a higher weight category. The two struggled through an even contest. Trailing 1-2, Merleni tied the score with 2 ½ minutes left and then was awarded the victory by judges' decision.
In 2008, at the Olympic Games in Beijing, Irini Merleni was competing in the under-48kg category. She faced Chiahru Icho in the semi-final, but her Japanese opponent won the bout that time. Merleni pulled herself back up, and found the motivation needed to beat America’s Clarissa Chun in the bronze medal match.